Hundreds were crowded around a Hindu temple at Nileshwaram in the southern state of Kerala on the evening of Oct 28 to watch the fireworks, videos posted by Indian newspapers showed.
Then, from inside a building, a surge of crackles could be heard, before a powerful ball of flame surged high into the sky.
“Around eight people are critical, and around 154 have been reported injured, out of which 97 people are admitted in hospital,” local police chief Shilpa Dyavaiah told AFP.
“They burst firecrackers very close to the place where they have stored the firecrackers,” Ms Dyavaiah said, adding that sparks from the burst crackers reached the cache.
Indian media reports, citing officials, said the blaze caused burns to the faces and hands of those in tightly packed crowd.
Local government official K. Inbasekhar said no permission had been given for the fireworks show.
The temple president and secretary had been taken into custody, The Hindu newspaper reported.
Religious gatherings in India have a grim track record of deadly incidents caused by safety lapses and poor crowd management.
In 2016, at least 112 people were killed after a huge explosion caused by a banned fireworks display at a temple marking the Hindu new year.
SD/